You can use Multi-level BOMs in BOM Insight via the inclusion of a Parent Part Number column in your BOM file and the correlation of that data creating a “Parent/Child” relationship with the “Customer Part Number” column.
To use a Multi-level BOM, first add your file as usual via the BOM settings page:
On the next page for Mapping, check the box for Multilevel BOM:
Once your BOM is loaded, you will see a Parent PN and Level columns to display your multi-level BOM. Additionally, you can open the left-side panel and click 'BOM Structure' for an easy to view tree of your levels:
You can review the article BOM Upload for more information in general about uploading BOMs.